Acute respiratory distress syndrome (ARDS) and acute lung injury (ALI) are medical conditions that occur when there is severe inflammation and increased fluids in both lungs, making it difficult for the lungs to function properly. Hospital treatment for a person with ALI/ARDS often includes the use of a breathing machine, or ventilator, until the person is able to breathe without assistance. Initiating proper nutrition through a feeding tube early in a person's hospital stay may help to improve recovery, but the optimal timing, composition, and amount of feeding treatments are unknown. This study will evaluate whether early or delayed full-calorie feeding through a feeding tube is more effective in reducing recovery time and increasing survival rates in people with ALI/ARDS. The study will also determine whether supplementing the feedings with omega-3 fatty acids and antioxidants benefits people with ALI/ARDS.